Update PETSc configure options for v2.0.0.
Fixed typo in help info.

Small improvements to help info.
Merge branch 'master' into baagaard/maint-1.9.0

* master:
  Fixed typo in help info.
  Update PETSc configure options for v2.0.0.
Revert PETSc settings after merge for v1.9.0.